xuyangzhong created CALCITE-4771:
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Summary: change the value of the CAST function to be nullable
Key: CALCITE-4771
URL: https://issues.apache.org/jira/browse/CALCITE-4771
Project: Calcite
Issue Type: Improvement
Reporter: xuyangzhong
In the sql "SELECT CAST('haha' AS INT)",the value the function CAST returns
will be parsed into NOT NULL, because when parsing, the type CAST returns is
from the INT and the nullable attribute is from the 'haha', which doesn't
consider the condition that parsing a string to an int could be invalid and
return NULL values.
I think there are two ways to improve this question:
* One is to change the value of the CAST function to be nullable, which avoids
the invalid parsing.
* The other way is to introduce a function named TRY_CAST, which is used in
SQL Server.If the parsing fails, TRY_CAST will return NULL instead of throws
exception that a NOT NULL field will be set with our unexpected value NULL.
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